calculate_lshell prototype is added.

pyspedas/geopack/calculate_lshell.py

@@ -0,0 +1,33 @@
+def calculate_lshell(sc_pos):
+    """
+    Calculate the L-shell value for spacecraft position data.
+
+    Parameters:
+    sc_pos (numpy.ndarray): Spacecraft position data array with columns [time, x, y, z]
+                            where time is in Unix timestamp, and x, y, z are in GSM coordinates.
+
+    Returns:
+    numpy.ndarray: L-shell values corresponding to the input spacecraft positions.
+    """
+    import numpy as np
+    import geopack.geopack as geopack
+
+    # Extracting the columns from the spacecraft position data
+    times, x, y, z = sc_pos[:, 0], sc_pos[:, 1], sc_pos[:, 2], sc_pos[:, 3]
+
+    lshell_values = []  # List to store the calculated L-shell values
+
+    for time, xi, yi, zi in zip(times, x, y, z):
+        # Recalculating geomagnetic dipole parameters
+        geopack.recalc(time)
+
+        # Tracing the magnetic field line from the position to the equator
+        xf, yf, zf, xx, yy, zz  = geopack.trace(xi, yi, zi, dir=-1, rlim=60., r0=1.,
+                                                      parmod=2, exname='t89', inname='igrf')
+
+        # Calculating the L-shell value as the radial distance at the equator
+        lshell = np.sqrt(xf ** 2 + yf ** 2 + zf ** 2)
+
+        lshell_values.append(lshell)
+
+    return np.array(lshell_values)